Recycling of distillery slops for ethanol and acetic acid production

A study on the recycling of distillery slops in molasses fermentation to produce ethanol and acetic acid was conducted. Back-slopping was carried out using a 25% slops solution for each cycle. There was no significant difference in the fermentation efficiencies obtained for the five recycles, which meant that the number of recycles had no adverse effect on fermentation efficiency. The use of back-slopping was able to cut the wastewater generated by 18.42%. It therefore reduced the water consumption in the distillery by approximately the same quantity. The unrecycled slops were then used in the production of acetic acid, which proved to be an effective and productive way of handling distillery slops. The efficiency of acetic acid production was 13.04% for the control setup and 10.22% for the treated sample. At the end of the fermentation, total acetic acid content of the treated sample and the control were 9.46 g and 10.50 g, respectively. These values were low compared with the standard set for commercial vinegar (40 g acetic acid for every liter). The low efficiencies and acid content were attributed to inadequate aeration during fermentation.